1. Field of the Invention
This invention generally relates to arm-mounted laser scanner systems for reading indicia of different light reflectivity such as bar code symbols and, more particularly, to so-called mirrorless scanner systems wherein system components, other than mirrors, are employed to effect sweeping or scanning of symbols to be read.
2. Description of Related Art
Laser scanner systems and components of the type exemplified by U.S. Pat. Nos. 4,251,798; 4,360,798; 4,369,361; 4,387,297; 4,593,186; 4,496,831; 4,409,470; 4,460,120; 4,607,156; 4,673,803; 4,736,095; 4,758,717; 4,816,660; 4,808,804; 4,816,661; 4,760,248; 4,871,904; 4,806,742; 4,845,350, as well as U.S. Appln. Ser. Nos. 148,669 and 147,708 --all of said patents and patent applications being owned by the assignee of the instant invention and being incorporated by reference herein --have generally been designed to read indicia having parts of different light reflectivity, e.g. bar code symbols, particularly of the Unversal Product Code (UPC) type, at a certain working or reading distance from a hand-held or stationary scanner.
Typically, a light source such as a laser generates a light beam which is optically modified to form a beam spot of a certain size at the working distance and is directed by optical components along a light path toward a bar code symbol located in the vicinity of the working distance for reflection from the symbol. A photodetector having a field of view extending across and slightly past the symbol detects light of variable intensity reflected off the symbol and generates electrical signals indicative of the detected light. These electrical signals are decoded into data descriptive of the symbol. A scanning component is situated in the light path. The scanning component may either sweep the beam spot across the symbol and trace a scan line across and past the symbol, or scan the field of view of the photodetector, or do both.
In any case, the scanner typically includes a moving mirror. For example, U.S. Pat. No. 4,251,798 discloses a rotating polygon having a planar mirror at each side, each mirror tracing a scan line across the symbol. U.S. Pat. Nos. 4,387,297 and 4,409,470 both employ a planar mirror which is repetitively and reciprocally driven in alternate circumferential directions about a drive shaft on which the mirror is mounted. U.S. Pat. No. 4,816,660 discloses a multi-mirror construction composed of a generally concave mirror portion and a generally planar mirror portion, the multi-mirror construction being repetitively and reciprocally driven in alternate circumferential directions about a drive shaft on which the multi-mirror construction was mounted.
No matter what the shape or orientation of the mirror, the known scanning components employed in laser scanning systems moved mirrors to perform the aforementioned sweeping and scanning actions. Moving other laser scanning system components was not thought to be practical. Thus, moving a gas laser tube was unthinkable, particularly in hand-held, compact system applications, due to the large size and the requisite large room necessary to accommodate a moving gas laser tube. Moving an optical lens was also not thought to be desirable, because optical alignment is critical in laser scanning systems. Hence, it was the mirror that was typically designated to effect the sweeping/scanning functions. However, in some laser scanning applications, mirror movements have not been found to be altogether desirable.
In non-laser scanning systems of the type exemplified by U.S. Pat. No. 4,578,571, a non-laser light emitting diode, an optical assembly, a photodetector, and electronic preamplifier/filter circuitry are all fixedly mounted on a common support that is connected to a cantilevered bimorph which is reciprocatingly driven to jointly move all the aforementioned components back and forth over a bar code symbol to be scanned. The large volume and heavy mass of all the commonly-mounted non-laser system components requires the expenditure of a great deal of power for the drive. This is not altogether practical in those cases, e.g. battery-powered operation, where power consumption is to be held to a minimum. Also, moving only one or more non-mirrored system components relative to another for conserving power was heretofore not considered desirable, because of the optical alignment problems described above.
The components for the light scanning system, including the light source, optics, photodetector, scanning component and an electrical conductor, are mounted together in a common assembly to constitute a compact, lightweight, scan module. The scan module is mounted in an interchangeable, modular manner in housings of different configurations.
For example, the housing can be hand-held and shaped as a cylinder in a so-called flashlight-type configuration, or shaped as a box, or shaped with a gun-like configuration. The housing can be mounted on the back of an operator's arm (see, for example, U.S. Pat. No. 4,766,299) or on one or more fingers of the operator's hand, typically with the aid of a strap, a clip, or a glove. The housing can be mounted on the operator's arm, typically adjacent or on the wrist. The housing can be mounted in a countertop workstation. The housing can be mounted in a mobile cart, or shopping cart, or, in some cases, even in a stationary installation.
The compact, lightweight nature of the scan module enables myriad other housing configurations to be fashioned. Thus, the scan module can be mounted anywhere on an operator's person, e.g. in a helmet to be worn on the operator's head, in eyeglasses to be worn in front of the operator's eyes, in a shoulder or body harness, etc.